1. Field of the Invention
This invention relates to an optical functional amplifying method and an optical functional amplifying device wherein an optical pulse train is controlled using a semiconductor laser amplifier. More particularly, the present invention relates to an optical functional amplifying method and an optical functional amplifying device by which a train of very short optical pulse with a very high repetition rate can be controlled and which is useful for optical communication, optical information processing, optical measurement and so forth.
2. Description of the Prior Art
In recent years, a demand for development of a technique for transmitting and controlling an optical pulse data train having a time width of several ps (picoseconds) or less and a repetition frequency exceeding several tens Gb/s to one hundred Gb/s as a basic technique for very high speed optical communication and optical information processing. Here, b/s represents a pulse amount per one second in units of a bit and 1 Gb/s corresponds to a pulse amount of 10.sup.9 bits per second.
In such a situation as described above, there is demand to establish, together with production of a stable and coherent optical pulse train, a technique for production of a very high speed optical pulse data train, a technique for dividing and extracting a very high speed optical pulse train and a technique for recovering the waveform of a very high speed optical pulse data train which has been distorted with respect to time during transmission. Of the techniques mentioned, there are available techniques for division and extraction of a very high speed optical pulse data train and for recovery of the waveform requiring gate switches which operate at a very high speed. In an ordinary case, electric control is very difficult due to the restriction in response speed, and therefore, an optical gate which is controlled by an optical pulse has been proposed for such gate switches.
One such optical gates is an interferometer wherein a semiconductor laser amplifier is disposed in an optical path. An interferometer of the type just mentioned is disclosed, for example, in I. Glesk et al., Electron. Lett, 30(4), 339-341(1994). The thesis recites a result of an experiment wherein an optical data train of 250 Gb/s was divided at the rate of 100 MHz using an optical loop type interferometer called TOAD (Terahertz optical asymmetric demodulation) by which a timeslot of 4 ps was realized.
With such a conventional optical gate employing an interferometer wherein a semiconductor laser amplifier is disposed in an optical path as described above, the operation repetition frequency depends upon the life of carriers in the semiconductor laser, and the gate operation at a repetition frequency exceeding several tens GHz is difficult. Accordingly, the conventional optical gate has a problem in that, while it can be used in an application wherein a gate operation approximately of picoseconds is performed in a comparatively low repetition frequency from a very high speed optical data train, it cannot be used in another application wherein a true very high speed gate operation is performed.